Extreme Low-Temperature High Strain-Rate Constitutive Behavior Evolution of Doped and Undoped Leadfree Solders under Sustained High Temperature Exposure

Electronics in automotive under-hood and aerospace applications may require sustained high temperature exposure in the range of 150-200°C in addition to mechanical shock and vibration. Electronics may be stored for prolonged duration in non-climate-controlled enclosures prior to deployment in the end application. In addition, electronics may be subjected to high strain rates at extreme low temperature and high temperature extremes. The effect of sustained high temperature storage on the high strain rate low-temperature performance are not well understood. In this paper SAC305, SAC-Q, SAC-R, and M758 solder are studies in a strain-rate range of 1-100 per sec in the temperature range of -65°C to +200°C after 8-months of sustained exposure to 50°C and 100°C. Doped solder alloys include addition of Ni, Co, Au, P, Ga, Cu and Sb to SAC solder alloy to boost the mechanical properties, thermal properties, wettability, melting temperature, shock and drop performance and solder alloy microstructure. The accuracy of Anand model has been quantified by comparing the experimentally measured data with the predicted data with the computed model constants. The Anand parameters have been implemented in an FE-framework to simulate the drop events for a ball-grid array package on printed circuit board assembly to determine hysteresis loop and plastic work density. Evolution in hysteresis loops and PWD have been studied and compared for various thermal aging durations and storage temperatures in addition to extreme operating temperatures.